Method for detecting leaks in an intake manifold

ABSTRACT

Methods and systems are provided for detecting leaks in an intake manifold of an engine. In one example, a method may include closing all intake valves of all cylinders of the engine during an engine shut down responsive to vacuum in the intake manifold reaching a pre-determined vacuum level. The method may further include indicating a leak in the intake manifold responsive to a change in a level of vacuum in the intake manifold after closing all the intake valves of all cylinders.

FIELD

The present description relates generally to detecting leaks in anintake manifold of an internal combustion engine.

BACKGROUND/SUMMARY

Leaner than desired air-fuel ratios in an engine may be caused byunmetered air entering the engine via leaks in an engine intakemanifold. For example, a leaky canister purge valve may allow additionalair into the engine intake manifold. Alternatively, a degraded mass airflow sensor may also result in leaner than desired engine conditions.Engine conditions with leaner than desired air-fuel ratios can degradeengine performance and increase emissions. Accordingly, variousapproaches may be employed to diagnose reasons for lean engineconditions.

Example diagnostic methods may include detecting degradation in the massair flow sensor, exhaust gas sensor, and/or leaks in the canister purgevalve. Another example diagnostic approach is shown by Schnaibel et al.in U.S. Pat. No. 6,886,399 wherein intake manifold pressure is monitoredto determine a leak in the intake manifold. Specifically, intakemanifold pressure is monitored after engine shut down and after anintake throttle is closed. Further, air flow into the intake manifoldfrom other sources such as an exhaust gas recirculation (EGR) valve anda canister purge valve is also terminated while monitoring changes inthe intake manifold pressure after engine shut down. If intake manifoldpressure increases at a rate higher than a pre-determined thresholdrate, a leak may be indicated.

The inventors herein have recognized potential issues with the exampleapproach in U.S. Pat. No. 6,886,399. As one example, the rate ofincrease in intake manifold pressure after engine shut down may bedifferent based on a position of each intake valve and/or exhaust valveof each cylinder. For example, if the engine shuts down with intake andexhaust valves of multiple cylinders in an open position, the cylindersand the intake manifold may be exposed to the atmosphere via the exhaustpassage. Herein, the rate of change in intake manifold pressure may besubstantially different relative to the rate of change in intakemanifold pressure when fewer cylinders are open to the atmosphere. Assuch, these differences in rate of change of intake manifold pressuremay cause errors in the diagnosis of leaks in the intake manifold. Toreduce such errors, a controller of the engine may be programmed withlook-up tables indicating an expected rate of change of intake manifoldbased on various positions of each intake valve and exhaust valve ofeach cylinder. Herein, the leakage diagnosis may be more complicated,more time consuming as well as having reduced efficiency.

In one example, the issues described above may be at least partlyaddressed by a method for an engine, comprising adjusting all intakevalves closed in each cylinder of the engine responsive to vacuum in anintake manifold reaching a pre-determined vacuum during engine shutdown, and indicating a leak in the intake manifold based on a change ina level of vacuum in the intake manifold. In this way, leaks in theintake manifold may be detected in a more reliable manner.

As an example, a leak check for an intake manifold in an engine may beinitiated during an anticipated engine shut down. As the engine spinsdown to rest, air flow into the intake manifold may be discontinued byclosing an intake throttle as well as other supplementary air flowsincluding exhaust gas recirculation, canister purge, etc. Piston motionin the cylinders of the engine may generate vacuum in the intakemanifold. The vacuum in the intake manifold may be monitored and once apre-determined vacuum level is reached, all intake valves of allcylinders of the engine may be adjusted closed. For example,electro-mechanical actuators may be utilized to close all the intakevalves. In another example, all exhaust valves of all cylinders of theengine may be adjusted closed. A change in the vacuum level in theintake manifold after closing all intake valves may indicate a leak.Specifically, a decrease in the vacuum level in the intake manifold mayindicate a leaky intake manifold.

In this way, leaks in the intake manifold may be determined in a simplermanner with higher accuracy. By closing all intake valves (or allexhaust valves) of all cylinders of the engine, the intake manifold maynot be exposed to the atmosphere and a desired level of vacuum may betrapped in the intake manifold each time the test is initiated. Further,by trapping the same desired level of vacuum in the intake manifold ateach leak test, more reliable results may be obtained. Further still,the leak test may be performed without relying on look-up tables fordifferent rates of change in intake manifold pressure. Overall, the leaktest may be less complex and may be performed more efficiently.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic engine.

FIG. 2 is a schematic layout of a hybrid vehicle system.

FIG. 3 illustrates a high level flow chart for initiating a leak test ofan intake manifold.

FIGS. 4A and 4B show a high level flow chart for performing the leaktest of the intake manifold, according to the present disclosure.

FIG. 5 is a high level flow chart of performing the leak test of theintake manifold in the hybrid vehicle system.

FIG. 6 illustrates an example leak test in the engine of a non-hybridvehicle.

FIG. 7 depicts an example leak test in the engine of a hybrid vehicle.

DETAILED DESCRIPTION

The following description relates to systems and methods for determiningleaks in an intake manifold of an engine system, such as the exampleengine system of FIG. 1. The engine system may be part of a hybridvehicle propulsion system, such as the hybrid vehicle system of FIG. 2.A leak test may be initiated in the engine responsive to lean engineconditions being detected in the engine (FIG. 3). As such, the leak testmay include generating a vacuum in the intake manifold as the engineshuts down to rest (FIGS. 4A, 4B) by closing an intake throttle as wellas terminating air flow from other sources. In response to vacuum in theintake manifold attaining a pre-determined level, all intake valves ofall cylinders of the engine may be fully closed. In a camless engine,the intake valves may be adjusted closed via an electro-mechanicalactuator. In a hybrid vehicle, the intake valves may be adjusted closedby rotating the engine (FIG. 5) using a generator in the hybrid vehiclesystem. Alternative approaches to sealing the engine from the atmospheremay be used such as additional valves etc. As such, vacuum in the intakemanifold may be held at substantially the pre-determined level unless aleak is present in the intake manifold. Herein, the leak is indicatedwhen vacuum in the intake manifold decreases below a threshold within athreshold period (FIG. 6). An example leak test for a hybrid vehiclesystem is depicted in FIG. 7.

Regarding terminology used herein, a vacuum may also be termed “negativepressure”. Both vacuum and negative pressure refer to a pressure lowerthan atmospheric pressure.

FIG. 1 depicts an example of a combustion chamber 14 or cylinder 14 ofinternal combustion engine 10. Engine 10 may be controlled at leastpartially by a control system including controller 12 and by input froma vehicle operator 130 via an input device 132. In this example, inputdevice 132 includes an accelerator pedal and a pedal position sensor 134for generating a proportional pedal position signal PP. Cylinder 14(herein also termed combustion chamber 14) of engine 10 may includecombustion chamber walls 136 with piston 138 positioned therein. Piston138 may be coupled to crankshaft 140 so that reciprocating motion of thepiston is translated into rotational motion of the crankshaft.Crankshaft 140 may be coupled to at least one drive wheel of thepassenger vehicle via a transmission system (not shown). Further, astarter motor (not shown) may be coupled to crankshaft 140 via aflywheel (not shown) to enable a starting operation of engine 10.

Cylinder 14 can receive intake air via intake passage 142 and intakemanifold 144. Intake passage 142 and intake manifold 144 can communicatewith other cylinders of engine 10 in addition to cylinder 14. In someexamples, one or more of the intake passages may include a boostingdevice such as a turbocharger or a supercharger (not shown).

Exhaust manifold 148 can receive exhaust gases from other cylinders ofengine 10 in addition to cylinder 14. Exhaust gas sensor 128 is showncoupled to exhaust passage 158 upstream of emission control device 178.Sensor 128 may be selected from among various suitable sensors forproviding an indication of exhaust gas air/fuel ratio such as a linearoxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), atwo-state oxygen sensor or EGO (as depicted), a HEGO (heated EGO), aNOx, HC, or CO sensor, for example. Emission control device 178 may be athree way catalyst (TWC), NOx trap, various other emission controldevices, or combinations thereof.

Each cylinder of engine 10 may include one or more intake valves and oneor more exhaust valves. For example, cylinder 14 is shown including atleast one intake poppet valve 150 and at least one exhaust poppet valve156 located at an upper region of cylinder 14. In some examples, eachcylinder of engine 10, including cylinder 14, may include at least twointake poppet valves and at least two exhaust poppet valves located atan upper region of the cylinder. Intake manifold 144 may be in fluidiccommunication with cylinder 14 via intake valve 150.

Intake valve 150 may be controlled by controller 12 via actuator 152.Similarly, exhaust valve 156 may be controlled by controller 12 viaactuator 154. During some conditions, controller 12 may vary the signalsprovided to actuators 152 and 154 to control the opening and closing ofthe respective intake and exhaust valves. The position of intake valve150 and exhaust valve 156 may be determined by respective valve positionsensors (not shown). Actuators 152 and 154 may be of the electric valveactuation type. In another example, actuators 152 and 154 may beelectro-mechanical actuators. As such, engine 10 may be a camlessengine. Herein, the opening and closing of the intake and exhaust valvesmay be performed in an electro-mechanical manner. Specifically, eachintake valve and each exhaust valve of each cylinder may be openedand/or closed independent of rotation of the crankshaft 140. In otherwords, each intake valve in the camless engine may be a camless intakevalve, and each exhaust valve of the camless engine may be a camlessexhaust valve. In an alternative example, engine 10 may include valveactuators that are of the cam actuation type, or a combination thereofto enable variable valve timing. For example, a hybrid vehicle system,such as that shown in FIG. 2, may include an engine which includescamshafts to control intake valves and exhaust valves. Alternatively,the hybrid vehicle system of FIG. 2 may include a camless engine.

In one example, cylinder 14 may alternatively include an intake valvecontrolled via electric valve actuation and an exhaust valve controlledvia cam actuation including cam profile switching (CPS), variable valvetiming (VVT), and/or variable cam timing (VCT). In other examples, theintake and exhaust valves may be controlled by a common valve actuatoror actuation system, or a variable valve timing actuator or actuationsystem.

Cylinder 14 can have a compression ratio, which is the ratio of volumeswhen piston 138 is at bottom center to top center. In one example, thecompression ratio is in the range of 9:1 to 10:1. However, in someexamples where different fuels are used, the compression ratio may beincreased. This may happen, for example, when higher octane fuels orfuels with higher latent enthalpy of vaporization are used. Thecompression ratio may also be increased if direct injection is used dueto its effect on engine knock.

In some examples, each cylinder of engine 10 may include a spark plug192 for initiating combustion. Ignition system 190 can provide anignition spark to combustion chamber 14 via spark plug 192 in responseto spark advance signal SA from controller 12, under select operatingmodes. However, in some embodiments, spark plug 192 may be omitted, suchas where engine 10 may initiate combustion by auto-ignition or byinjection of fuel as may be the case with some diesel engines.

In some examples, each cylinder of engine 10 may be configured with oneor more fuel injectors for providing fuel thereto. As a non-limitingexample, cylinder 14 is shown including fuel injector 166. Fuel injector166 may be configured to deliver fuel received from fuel system 40. Fuelinjector 166 is shown coupled directly to cylinder 14 for injecting fueldirectly therein in proportion to the pulse width of signal FPW receivedfrom controller 12 via electronic driver 169. In this manner, fuelinjector 166 provides what is known as direct injection of fuel intocylinder 14. While FIG. 1 shows fuel injector 166 positioned to one sideof cylinder 14, it may alternatively be located overhead of the piston,such as near the position of spark plug 192. Such a position may improvemixing and combustion when operating the engine with an alcohol-basedfuel due to the lower volatility of some alcohol-based fuels.Alternatively, the injector may be located overhead and near the intakevalve to improve mixing. Fuel may be delivered to fuel injector 166 froma fuel tank of fuel system 40 via a high pressure fuel pump, and a fuelrail. Further, the fuel tank may have a pressure transducer providing asignal to controller 12.

In some embodiments, combustion chamber 14 may alternatively oradditionally include a fuel injector arranged in intake manifold 144 ina configuration that provides what is known as port injection of fuelinto the intake port upstream of combustion chamber 14.

Intake manifold 144 is shown communicating with intake throttle 162having a throttle plate 164. In this particular example, the position ofthrottle plate 164 may be varied by controller 12 via a signal providedto an electric motor or actuator (not shown in FIG. 1) included withintake throttle 162, a configuration that is commonly referred to aselectronic throttle control (ETC). Intake throttle position may bevaried by the electric motor via a shaft. Intake throttle 162 maycontrol airflow from intake passage 142 to intake manifold 144 andcombustion chamber 14 (and other engine cylinders). The position ofthrottle plate 164 may be provided to controller 12 by throttle positionsignal TP from throttle position sensor 163.

Further, in the disclosed embodiment, an exhaust gas recirculation (EGR)system may route a desired portion of exhaust gas from the exhaustpassage 158 to the intake manifold 144 via an EGR passage 176. Theamount of EGR provided may be varied by controller 12 via an EGR valve174. By introducing exhaust gas to the engine 10, the amount ofavailable oxygen for combustion is decreased, thereby reducingcombustion flame temperatures and reducing the formation of NO_(x), forexample. Under some conditions, the EGR system may be used to regulatethe temperature of the air and fuel mixture within the combustionchamber, thus providing a method of controlling the timing of ignitionduring some combustion modes. Further, during some conditions, a portionof combustion gases may be retained or trapped in the combustion chamberby controlling exhaust valve timing, such as by controlling a variablevalve timing mechanism.

Fuel system canister 22 (also termed canister 22) is fluidically coupledto one or more fuel tanks of fuel system 40. Canister 22 may be filledwith an appropriate adsorbent for temporarily trapping fuel vapors(including vaporized hydrocarbons) generated during fuel tank refuelingoperations, as well as diurnal vapors. In one example, the adsorbentused is activated charcoal. When canister purging conditions are met,such as when the canister is saturated, vapors stored in fuel systemcanister 22 may be purged to intake manifold 144, via purge line 182 byopening canister purge valve 168. The purged fuel vapors may then bedrawn into cylinder 14 for combustion. While a single canister 22 isshown, it will be appreciated that fuel system 40 may include any numberof canisters.

Canister 22 further includes a vent line 184 (herein also referred to asa fresh air line) for routing gases out of the canister 22 to theatmosphere when storing, or trapping, fuel vapors from fuel tanks offuel system 40. Vent line 184 may also allow fresh air to be drawn intofuel system canister 22 when purging stored fuel vapors to intakemanifold 144 via purge line 182 and canister purge valve 168. Vent line184 may include a canister vent valve 186 to adjust a flow of air andvapors between canister 22 and the atmosphere. The canister vent valvemay also be used for diagnostic routines. When included, the vent valvemay be opened during fuel vapor storing operations (for example, duringfuel tank refueling and while the engine is not running) so that air,stripped of fuel vapors after having passed through the canister, can bepushed out to the atmosphere. Likewise, during purging operations (forexample, during canister regeneration and while the engine is running),the vent valve may be opened to allow a flow of fresh air to strip thefuel vapors stored in the canister. By closing canister vent valve 186,the fuel tank(s) may be isolated from the atmosphere during a fuelsystem leak test.

As described above, FIG. 1 shows only one cylinder of a multi-cylinderengine. As such, each cylinder may similarly include its own set ofintake/exhaust valves, fuel injector(s), spark plug, etc. It will beappreciated that engine 10 may include any suitable number of cylinders,including 2, 3, 4, 5, 6, 8, 10, 12, or more cylinders. Further, each ofthese cylinders can include some or all of the various componentsdescribed and depicted by FIG. 1 with reference to cylinder 14. Furtherstill, engine 10 may be an inline-cylinder engine with its cylindersarranged in an inline manner. Alternatively, the cylinders of engine 10may be arranged in a V-manner and engine 10 may be one of a V-6, V-8,V-12, etc. engine.

Controller 12 is shown in FIG. 1 as a microcomputer, includingmicroprocessor unit 106, input/output ports 108, an electronic storagemedium for executable programs and calibration values shown asnon-transitory read only memory chip 110 in this particular example forstoring executable instructions, random access memory 112, keep alivememory 114, and a data bus. Controller 12 may receive various signalsfrom sensors coupled to engine 10, in addition to those signalspreviously discussed, including measurement of inducted mass air flow(MAF) from mass air flow sensor 122; engine coolant temperature (ECT)from temperature sensor 116 coupled to cooling sleeve 118; a profileignition pickup signal (PIP) from Hall effect sensor 120 (or other type)coupled to crankshaft 140; throttle position (TP) from a throttleposition sensor; and absolute manifold pressure signal (MAP) from sensor124. Engine speed signal, RPM, may be generated by controller 12 fromsignal PIP. Manifold pressure signal MAP from a manifold pressure sensormay be used to provide an indication of vacuum, or pressure, in theintake manifold.

Controller 12 may also receive input from gear selector 170. A vehicleoperator 130 may adjust a gear of the transmission by adjusting theposition of gear selector 170. In one example, as depicted gear selector170 may have 5 positions (PRNDL gear selector), however, otherembodiments may also be possible. As known in the art, selecting P gearrepresents a parked position for a vehicle while gear D indicates thatthe vehicle can be driven.

The controller 12 may receive signals from the various sensors of FIG. 1and employ the various actuators of FIG. 1 to adjust engine operationbased on the received signals and instructions stored on a memory of thecontroller. Example actuators include EGR valve 174, fuel injector 166,canister purge valve 168, and intake throttle 162. In a camless engine,additional example actuators may include electro-mechanical actuatorsthat control the opening and/or closing of all intake and exhaust valvesof all cylinders. The controller 12 may receive input data from thevarious sensors, process the input data, and trigger the actuators inresponse to the processed input data based on instruction or codeprogrammed therein corresponding to one or more routines, such asexample control routines described herein with regard to FIGS. 3, 4A and4B, and 5.

FIG. 2 is a schematic depiction of an example vehicle propulsion system200. Vehicle propulsion system 200 includes a fuel burning engine 10 anda motor 220. As a non-limiting example, engine 10 comprises an internalcombustion engine and motor 220 comprises an electric motor. As such,engine 10 included in vehicle propulsion system 200 may be the same asengine 10 of FIG. 1. Therefore, some components introduced previously inreference to FIG. 1 may be numbered similarly.

Motor 220 may be configured to utilize or consume a different energysource than engine 10. For example, engine 10 may consume a liquid fuel(e.g. gasoline) to produce an engine output while motor 220 may consumeelectrical energy to produce a motor output. As such, a vehicle withpropulsion system 200 may be referred to as a hybrid electric vehicle(HEV). Specifically, the propulsion system 200 depicted herein is aplug-in hybrid electric vehicle (PHEV). PHEVs are also classified aspartial zero emissions vehicles (PZEVs) due to their substantiallyreduced exhaust emissions.

Vehicle propulsion system 200 may be operated in a variety of differentmodes depending on vehicle operating conditions. Some of these modes mayenable engine 10 to be maintained in an off state (or deactivated state)where combustion of fuel at the engine is discontinued. For example,under select operating conditions, motor 220 may propel the vehicle viadrive wheel 232 while engine 10 is deactivated.

During other operating conditions, engine 10 may be deactivated whilemotor 220 is operated to charge energy storage device 250 viaregenerative braking. Therein, motor 220 may receive wheel torque fromdrive wheel 232 and convert the kinetic energy of the vehicle toelectrical energy for storage at energy storage device 250. Thus, motor220 can provide a generator function in some embodiments. However, inother embodiments, a dedicated energy conversion device, hereingenerator 260, may instead receive wheel torque from drive wheel 232 andconvert the kinetic energy of the vehicle to electrical energy forstorage at energy storage device 250. Energy storage device 250 may be,for example, a system battery or set of batteries.

During still other operating conditions, engine 10 may be operated bycombusting fuel received from fuel system 40. For example, engine 10 maybe operated to propel the vehicle via drive wheel 232 while motor 220 isdeactivated. During other operating conditions, both engine 10 and motor220 may each be operated to propel the vehicle via drive wheel 232. Aconfiguration where both the engine and the motor may selectively propelthe vehicle may be referred to as a parallel type vehicle propulsionsystem. Note that in some embodiments, motor 220 may propel the vehiclevia a first set of drive wheels and engine 10 may propel the vehicle viaa second set of drive wheels.

In other embodiments, vehicle propulsion system 200 may be configured asa series type vehicle propulsion system, whereby the engine does notdirectly propel the drive wheels. Rather, engine 10 may be operated topower motor 220, which may in turn propel the vehicle via drive wheel232. For example, during select operating conditions, engine 10 maydrive generator 260, which may in turn supply electrical energy to oneor more of motor 220 or energy storage device 250. As another example,engine 10 may be operated to drive motor 220 which may in turn provide agenerator function to convert the engine output to electrical energy,where the electrical energy may be stored at energy storage device 250for later use by the motor. The vehicle propulsion system may beconfigured to transition between two or more of the operating modesdescribed above depending on operating conditions.

Fuel system 40 may include one or more fuel storage tanks 244 forstoring fuel on-board the vehicle and for providing fuel to engine 10.For example, fuel tank 244 may store one or more liquid fuels, includingbut not limited to: gasoline, diesel, and alcohol fuels. In someexamples, the fuel may be stored on-board the vehicle as a blend of twoor more different fuels. For example, fuel tank 244 may be configured tostore a blend of gasoline and ethanol (e.g., E10, E85, etc.) or a blendof gasoline and methanol (e.g., M10, M85, etc.), whereby these fuels orfuel blends may be delivered to engine 10. Still other suitable fuels orfuel blends may be supplied to engine 10, where they may be combusted atthe engine to produce an engine output. The engine output may beutilized to propel the vehicle and/or to recharge energy storage device250 via motor 220 or generator 260.

Fuel tank 244 may include a fuel level sensor 246 which may comprise afloat connected to a variable resistor for sending a signal regarding afuel level in the tank to controller 12. The level of fuel stored atfuel tank 244 (e.g., as identified by the fuel level sensor) may becommunicated to the vehicle operator, for example, via a fuel gauge orindication lamp (not shown) on a dashboard of the vehicle system.

Vehicle propulsion system 200 may include a fuel door 262 located on anouter body of the vehicle for receiving fuel from an external fuelsource. Fuel door 262 may be held locked during most vehicle operatingconditions so as to contain fuel tank vapors and reduce the release offuel tank hydrocarbons into the environment. Fuel system 40 mayperiodically receive fuel from the external fuel source. However, sinceengine 10 is periodically set to a deactivated state (or engine-offmode) where the consumption of fuel at the engine is significantlyreduced or discontinued, long durations may elapse between subsequentfuel tank refilling events. During fuel tank refilling, fuel may bepumped into the fuel tank from fuel dispensing device 275 via arefueling line 248 that forms a passageway from fuel door 262.

Fuel vapors generated in fuel tank 244 due to diurnal events andrefueling events may be directed to and stored in canister 22. Thecanister may include an adsorbent for storing the received fuel vapors.During selected engine operating conditions, fuel vapors may be desorbedfrom the canister and released into an engine intake for purging.

Vehicle propulsion system 200 may include an auxiliary system 265. Theauxiliary system may be, for example, a vehicle navigation system (suchas a GPS), or an entertainment system (e.g., radio, DVD player, stereosystem, etc.). In one example, where auxiliary system is a vehiclenavigation system, location and time data may be transmitted between thecontroller 12 of the vehicle and a global positioning satellite viawireless communication.

Controller 12 may communicate with one or more of engine 10, motor 220,fuel system 40, energy storage device 250, and generator 260.Specifically, controller 12 may receive feedback from one or more ofengine 10, motor 220, fuel system 40, energy storage device 250, andgenerator 260 and send control signals to one or more of them inresponse. Controller 12 may also receive an indication of an operatorrequested output of the vehicle propulsion system from a vehicleoperator 130. For example, controller 12 may receive feedback from pedalposition sensor 134 which communicates with accelerator pedal 132. Pedal132 may refer schematically to an accelerator pedal (as shown) or abrake pedal.

Energy storage device 250 may include one or more batteries and/orcapacitors. Energy storage device 250 may be configured to storeelectrical energy that may be supplied to other electrical loadsresiding on-board the vehicle (other than the motor), including a cabinheating and air conditioning system (e.g., HVAC system), an enginestarting system (e.g., starter motor), headlights, cabin audio and videosystems, etc.

Energy storage device 250 may periodically receive electrical energyfrom an external power source 280 not residing in the vehicle. As anon-limiting example, vehicle propulsion system 200 may be configured asa plug-in hybrid electric vehicle (HEV), whereby electrical energy maybe supplied to energy storage device 250 from power source 280 via anelectrical energy transmission cable 282. During a recharging operationof energy storage device 250 from power source 280, electricaltransmission cable 282 may electrically couple energy storage device 250and power source 280. While the vehicle propulsion system is operated topropel the vehicle, electrical transmission cable 282 may bedisconnected between power source 280 and energy storage device 250.

In other embodiments, electrical transmission cable 282 may be omitted,where electrical energy may be received wirelessly at energy storagedevice 250 from power source 280. For example, energy storage device 250may receive electrical energy from power source 280 via one or more ofelectromagnetic induction, radio waves, and electromagnetic resonance.As such, it should be appreciated that any suitable approach may be usedfor recharging energy storage device 250 from the external power source280. In this way, motor 220 may propel the vehicle by utilizing anenergy source other than the fuel utilized by engine 10.

In some embodiments, engine 10 may be configured for selectivedeactivation. For example, engine 10 may be selectively deactivatableresponsive to idle-stop conditions. Therein, responsive to any or all ofidle-stop conditions being met, the engine may be selectivelydeactivated by deactivating cylinder fuel injectors. As such, idle-stopconditions may be considered met if the engine is combusting while asystem battery (or energy storage device) is sufficiently charged, ifauxiliary engine loads (e.g., air conditioning requests) are low, enginetemperatures (intake temperature, catalyst temperature, coolanttemperature, etc.) are within selected temperature ranges where furtherregulation is not required, and a driver requested torque or powerdemand is sufficiently low. In response to idle-stop conditions beingmet, the engine may be selectively and automatically deactivated viadeactivation of fuel and spark. The engine may then start to spin torest.

During engine shutdown, the engine may be spun to, and shutdown in, aselected position that improves engine restart e.g. a hot start. Forexample, one of the cylinders may be positioned such that it is in acompression stroke. Thus, when the controller determines that an enginerestart is imminent, fuel is injected into this cylinder and the air andfuel mixture is ignited to provide immediate response. In anotherexample, if a cold start is anticipated, the engine may be rotated to adifferent position from that used for the hot start. For example, thecylinders may be positioned such that one or more exhaust valves arefully closed to enable a reduced pressure in the intake manifold at asubsequent cold start.

Leaner than desired engine conditions may occur in engine 10 whenunmetered air leaks into the intake manifold of engine 10. Sources ofsuch unmetered air can include a degraded EGR valve, a degraded CPV,degradation in related hoses etc. Leaner than desired engine conditionsmay also occur due to a degraded MAF sensor and/or degradation in an EGOsensor. As such, leaks in the intake manifold may also allow unmeteredair into the engine. Leaks in the intake manifold can be diagnosed bygenerating a desired vacuum level in the intake manifold during anengine shut down and monitoring for a change in the vacuum level afterthe intake manifold is isolated from the atmosphere by closing eitherall intake valves of all cylinders or all exhaust valves of allcylinders of the engine. The leak test may be initiated only afterleaner than desired engine conditions are detected in the engine, asshown below in reference to FIG. 3.

FIG. 3 includes an example routine 300 for determining initiation of aleak test for an intake manifold of an engine, such as engine 10 ofFIGS. 1 and 2. As such, routine 300 will be described with relation tothe systems shown in FIGS. 1 and 2, but it should be understood thatsimilar routines may be used with other systems without departing fromthe scope of this disclosure. Specifically, the leak test is initiatedby routine 300 only after leaner than desired engine conditions aredetected. In other words, if the air-fuel ratio in the engine issubstantially at a desired ratio, the leak test for the intake manifoldmay not be activated.

Instructions for carrying out routine 300 and the rest of the routinesincluded herein (e.g., routines 400 and 500) may be executed by acontroller, such as controller 12 of FIGS. 1 and 2, based oninstructions stored on a memory of the controller and in conjunctionwith signals received from sensors of the engine system, such as thesensors described above with reference to FIG. 1. The controller mayemploy engine actuators of the engine system to adjust engine operation,according to the routines described below.

At 302, routine 300 estimates existing engine operating conditions.Operating conditions may be measured, estimated, or inferred, and mayinclude conditions such as engine speed, engine load, air-fuel ratio,MAP, as well as vehicle conditions, such as, fuel level, fuel vaporcanister load status, etc. Next, at 304, routine 300 determines whethera lean engine condition has been detected. A lean engine condition maybe determined based on the output of an EGO sensor. A lean enginediagnostic code may be set if the sensor output indicates that anexhaust oxygen content is above a threshold for a previously determinedduration. If a lean engine condition is not detected, routine 300proceeds to 306 to maintain engine conditions. Routine 300 may then end.

If however, a lean engine condition is confirmed at 304, routine 300progresses to 308 to determine that a leak test for the intake manifold(IM) is desired at a following engine shut down. Specifically, routine300 determines that the leak test for the intake manifold be activatedwhen the engine shuts down following the detection of the lean enginecondition. The leak test for the intake manifold is described inreference to FIGS. 4A and 4B below. Routine 300 then ends. Turning nowto FIGS. 4A and 4B, they depict routine 400 illustrating the leak testfor the intake manifold in accordance with the present disclosure. Assuch, routine 400 may be activated after a lean engine condition isdetected, such as by routine 300 of FIG. 3.

Routine 400 will be described with relation to the systems shown inFIGS. 1 and 2, but it should be understood that similar routines may beused with other systems without departing from the scope of thisdisclosure. Specifically, a pre-determined level of vacuum is generatedin the intake manifold of the engine and a change in the level of thevacuum is monitored for detecting leaks. The pre-determined level ofvacuum is generated during engine shut down to rest by closing an intakethrottle, an EGR valve, a CPV, etc. Once the pre-determined level ofvacuum is reached, all intake valves of all cylinders of the engine areadjusted (and maintained) closed to maintain the pre-determined level ofvacuum. If a leak is present in the intake manifold, the vacuum level inthe intake manifold reduces from the pre-determined level.

At 402, routine 400 determines if the engine is activated and “ON”. Assuch, the engine may be rotating and combusting when “ON”. If it isdetermined that the engine is not activated, routine 400 continues to404 to maintain the existing engine status and then ends. As such, theengine may not be activated when it is shut down and at rest. Forexample, in a hybrid vehicle, the engine may be “OFF” and may bedeactivated when the hybrid vehicle is being propelled primarily by amotor. In a vehicle where the engine is equipped with an idle-stopsystem (also termed, a start-stop system), the engine may be deactivatedwhen the vehicle is stopped, e.g. at a traffic light.

If the engine is activated and “ON”, routine 400 proceeds to 406 todetermine if an engine shut down is anticipated. In one example, anengine shut down to rest may be anticipated when a vehicle operatorshifts the gear selector (e.g., gear selector 170 in FIG. 1) to “Park”from a “Drive” position. In another example, engine shut down may beanticipated when the vehicle operator shifts the gear selector from anon-parked position (e.g. reverse gear position, neutral gear position,drive gear position) to a parked position (e.g. park gear position).Herein, the impending engine shut down may be followed by a key-offevent wherein the engine spins to rest. In another example, such as in avehicle equipped with an idle-stop system, an imminent engine shut downmay be expected when the engine idles for a duration longer than athreshold duration. In yet another example, the engine in the hybridvehicle may be shut down when the vehicle is operated on city streetswith repetitive stops and starts.

If an engine shut down is not impending, routine 400 continues to 404 tomaintain existing engine conditions including valve positions, and thenends. On the other hand, if engine shut down is imminent, routine 400continues to 408 to adjust various valves for the leak test of theintake manifold. Herein, the various valves are adjusted to discontinueair flow into the intake manifold.

Accordingly, at 410, the intake throttle is adjusted closed. In oneexample, the intake throttle may be adjusted to a fully closed positionfrom a partly open position. In another example, the intake throttle maybe moved to the fully closed position from a mostly open position. Assuch, the intake throttle is transitioned to the fully closed positionat 410 so that intake air does not flow into the intake manifold fromthe intake passage. Accordingly, intake air flow into the intakemanifold via the intake throttle may be discontinued. Further, at 412,the canister purge valve (CPV) may also be adjusted closed, if open.Accordingly, stored fuel vapors from the fuel system canister may not bepurged into the intake manifold. Next, at 414, the exhaust gasrecirculation (EGR) valve may be adjusted closed. Therefore, exhaustgases from the exhaust passage may no longer be received in the intakemanifold. Additional valves that enable air flow into the intakemanifold (not specifically listed here) may also be closed. For example,crankcase ventilation flow into the intake manifold may be discontinued.Other sources of air flow into the intake manifold may also be closed.Thus, the intake manifold may now be fluidically coupled to theatmosphere primarily via an open intake valve or an open exhaust valveof a cylinder of the engine.

It will be noted that pistons within the cylinders may continue toreciprocate as the engine spins down to rest. Since the various valvesallowing air into the intake manifold are now substantially closed,piston motion in the cylinders builds vacuum in the intake manifold, asat 416 of routine 400. Vacuum in the intake manifold may also be termedmanifold vacuum, also termed as Man Vac. At 418, routine 400 confirms ifvacuum in the intake manifold is at (or higher than) a pre-determinedlevel, Threshold_P. Pressure in the intake manifold (positive ornegative) may be estimated by an MAP sensor. In one example, thepre-determined level of vacuum (or negative pressure) may be 10 inchesof mercury. In another example, the pre-determined level of vacuum,Threshold_P, may be 12 inches of mercury. The pre-determined level ofvacuum may be selected based on the engine parameters including enginesize, number of cylinders, etc. Furthermore, the pre-determined vacuumlevel, Threshold_P, for a non-hybrid vehicle may be different from apre-determined vacuum level for a hybrid vehicle. Other levels ofpre-determined vacuum may be used without departing from the scope ofthis disclosure.

If it is determined that the vacuum in the intake manifold is not yet atthe pre-determined vacuum, Threshold_P, routine 400 proceeds to 420 tocontinue to increase vacuum levels in the intake manifold. Vacuum levelsin the intake manifold may continue to increase as the engine spins downto rest. Specifically, piston motion in the cylinders of the engine maybuild vacuum in the intake manifold as long as the intake manifold is influidic communication with the cylinders of the engine when the intakevalves are open during the cylinder cycle. Thus, the intake valves ofall cylinders of the engine may not be closed to enable build-up ofvacuum in the intake manifold.

However, if at 418, it is confirmed that the vacuum in the intakemanifold is at (or higher than) the pre-determined vacuum level,Threshold_P, routine 400 progresses to 422. At 422, it is determined ifthe vehicle is a hybrid vehicle or if the vehicle is equipped with astart-stop system. Vehicles equipped with the start-stop system orhybrid vehicles may include a generator and/or a motor that can rotatethe engine such that a desired position of intake and/or exhaust valvesis attained. If the vehicle is neither a hybrid vehicle nor equippedwith the start-stop system, the engine may include intake valves and/orexhaust valves that are actuated independent of crankshaft rotation. Forexample, the intake valves and/or the exhaust valves may be actuated byelectro-mechanical actuators, as described earlier in reference toFIG. 1. The engine may be a camless engine.

If it is determined that the vehicle is equipped with the start-stopsystem or that the vehicle is a hybrid vehicle, routine 400 progressesto 424 wherein routine 500 of FIG. 5 is activated. Routine 500 will bedescribed further below in reference to FIG. 5. Routine 400 then ends.However, if the vehicle is not a hybrid vehicle or does not include thestart-stop system, routine 400 continues to 426 to adjust all intakevalves of all cylinders of the engine to the fully closed position.Alternatively, all exhaust valves of all cylinders of the engine may beadjusted to their fully closed position. In another example, a mix ofintake valves and exhaust valves of the engine cylinders may be shiftedto their fully closed positions such that each cylinder of the engine issealed from the atmosphere (e.g., the exhaust passage). At 428,electro-mechanical actuators may be commanded to fully close all theintake valves of each cylinder of the engine. In another example,electro-mechanical actuators may be commanded to fully close all theexhaust valves of each cylinder of the engine. Specifically, eachcylinder may be isolated from the atmosphere by closing all intake (orall exhaust) valves of all cylinders. Further still, the intake manifoldmay also be isolated from the atmosphere by closing all intake (or allexhaust) valves of all cylinders of the engine. Furthermore, vacuumtrapped in the intake manifold may be at the pre-determined level,Threshold_P.

It will be noted that the engine may continue to spin down to rest afterthe intake valves are closed. Thus, the intake valves (and/or exhaustvalves) may be adjusted to their fully closed position during engineshut down to rest. In other words, the intake valves (and/or exhaustvalves) may be adjusted to their fully closed position before the engineshuts down to rest. However, the controller may be maintained activeeven after engine shut down (with engine at rest) to monitor for leaksin the intake manifold.

Next, at 430, routine 400 monitors the vacuum level in the intakemanifold for a pre-determined duration, D. The pre-determined duration Dmay, in one example, be 15 seconds. In another example, pre-determinedduration D may be 10 seconds. In yet another example, pre-determinedduration may be 60 seconds. Longer or shorter durations may be employedwithout departing from the scope of this disclosure. Next, at 432routine 400 determines if there is a change in the vacuum level in theintake manifold. As such, the vacuum level may have changed from thepre-determined vacuum level in the pre-determined duration D.Specifically, routine 400 confirms if the vacuum in the intake manifoldhas decreased below a threshold level, Threshold_L, at 432, within thepre-determined duration D, and after all intake valves (or all exhaustvalves) of all cylinders are fully closed. One or more leaks in theintake manifold may draw air into the intake manifold causing a decreasein the level of vacuum from the pre-determined vacuum level within theintake manifold. Threshold_L may be a level of vacuum that is lower thanthe pre-determined vacuum level, Threshold_P. In terms of pressure,Threshold_L may be higher than Threshold_P.

Accordingly, if vacuum in the intake manifold is lower than thethreshold level, Threshold_L, within pre-determined duration D, routine400 proceeds to 436 to indicate a leak in the intake manifold.Specifically, a malfunction indicator lamp (MIL) may be activated at 438at the next key-on event. Though not specifically shown, the controllermay adjust one or more of fuel injection amount and fuel injectiontiming responsive to the detection of the intake manifold leak duringsubsequent engine operation.

On the other hand, if the vacuum level in the intake manifold is higherthan the threshold level, Threshold_L, in pre-determined duration D,routine 400 progresses to 434 to determine that intake manifold leaksare not present. Further still, additional diagnostic routines may betriggered to diagnose reasons for lean engine conditions. The leak testof the intake manifold may thus be completed.

Next at 440, routine 400 determines if vacuum is leftover in the intakemanifold after completion of the leak test. Completion of the leak testmay include indicating a leak in the intake manifold or not indicating aleak in the intake manifold. For example, sufficient vacuum may residein the intake manifold after the intake manifold leak test, if there areno leaks in the intake manifold. In some examples, a certain amount ofvacuum may be trapped in the intake manifold even if the preceding leaktest indicates a leak in the intake manifold.

If a sufficient amount of vacuum is leftover in the intake manifold,routine 400 continues to 444 to apply the leftover vacuum to the fuelsystem for a leak test in the fuel system. Since the intake manifoldcontains vacuum, a negative pressure engine-off leak test may beperformed. Herein, the vacuum may be applied to the fuel systemincluding the canister by opening the CPV. Once a threshold level ofvacuum is attained in the fuel system, the CPV may be closed, and thefuel system may be monitored for changes in the level of vacuum. Oncethe fuel system leak test is completed, routine 400 proceeds to 446 torestore the positions of all valves. For example, the intake throttlemay be adjusted to a partly open position from the fully closedposition. The intake valves (and/or exhaust valves) may be adjusted to amore open position.

If sufficient vacuum is not remaining in the intake manifold aftercompletion of the intake manifold leak test, routine 400 continues to442 and the fuel system leak test may not be activated. Further, at 442,all valves may be restored to their desired positions. For example, theintake throttle may be adjusted to a partly open position from the fullyclosed position. The intake valves (and/or exhaust valves) may beadjusted to a more open position.

Thus, an example method for an engine may comprise adjusting all intakevalves closed in each cylinder of the engine responsive to vacuum in anintake manifold reaching a pre-determined vacuum (e.g., Threshold_P ofroutine 400) during engine shut down, and indicating a leak in theintake manifold based on a change in a level of vacuum in the intakemanifold. The change in the level of vacuum in the intake manifold mayinclude a decrease in the level of vacuum from the pre-determinedvacuum. Further, the leak may be indicated when the level of vacuumdecreases to below a threshold level (e.g., Threshold_L). The vacuum inthe intake manifold may be produced by closing an intake throttle anddiscontinuing flow of air into the intake manifold. Further, the intakethrottle may be closed in response to determining an impending engineshut down. Further still, the impending engine shut down may bedetermined, in one example, when a gear selector is shifted to a parkedposition. The method may further comprise producing vacuum in the intakemanifold by closing each of an exhaust gas recirculation valve and acanister purge valve in response to the impending engine shut down. Allintake valves of each cylinder of the engine may be closed via anelectro-mechanical actuator. The method may also comprise applyingleftover vacuum in the intake manifold to a fuel system for a leak checkin the fuel system after indicating the leak in the intake manifold.

Turning now to FIG. 5, it shows routine 500 for continuing the leak testof the intake manifold in a hybrid vehicle or a vehicle equipped with astart-stop system. Specifically, routine 500 may be activated as part ofroutine 400 if it is determined that the engine of FIG. 1 is included ina hybrid vehicle or a vehicle system equipped with a start-stop system.As such, routine 500 may commence only after 418 in routine 400. Toelaborate, routine 500 is activated in the hybrid vehicle or the vehicleequipped with a start-stop system after it is confirmed that the vacuumin the intake manifold is at the pre-determined level, Threshold_P.

At 502, routine 500 confirms that the vehicle is a hybrid vehicle or isalternatively a vehicle equipped with a start-stop (or idle stop)system. Each of the hybrid vehicle and the vehicle equipped with thestart-stop system may include a motor supplied by an energy storagedevice. Further, the motor may be utilized to rotate the engine(specifically, a crankshaft) to a desired position wherein all intakevalves and exhaust valves of the cylinders may be closed.

If it is not confirmed that the vehicle is a hybrid vehicle or isalternatively equipped with a start-stop (or idle stop) system, routine500 proceeds to 504 to return to 426 of routine 400, and then routine500 ends. As such, routine 400 may then be continued. If, however, it isconfirmed that the vehicle is a hybrid vehicle or is equipped with astart-stop (or idle stop) system, routine 500 continues to 506 to usethe motor in the vehicle system to rotate the engine. In one example, ahybrid vehicle may include two motors (or a motor and a generator) suchthat a first motor may propel the vehicle while the engine is shut downwhile a second motor can rotate the engine to a desired position. Itwill be noted that a vehicle with the start-stop system may also includea motor to enable engine rotation. Specifically, the motor may beemployed to rotate the engine (e.g., the crankshaft) to close all intakevalves of all cylinders of the engine. Alternatively, the motor mayrotate the crankshaft to close all exhaust valves of all cylinders ofthe engine. In one example, the motor may adjust the position of theengine only after the engine is at rest. Specifically, the crankshaftmay be rotated only after the engine has come to rest.

To elaborate, all the intake valves or all the exhaust valves may beadjusted to their respective fully closed positions (e.g., from an openposition) by adjusting the position of the crankshaft. Herein, thecrankshaft may be rotated in a forward direction or a backwarddirection, at 508, to close the intake valves and/or the exhaust valves.In one example, the engine may be rotated in the forward direction. Inanother example, the engine may be rotated in the backward direction.The choice of rotating the engine (specifically, the crankshaft) ineither the forward direction or the backward direction may be dependenton the position of the crankshaft when the engine comes to rest.Further, the selection of direction of rotation of the engine may alsobe based on which direction offers a quicker adjustment to enableclosing all the intake valves (or all the exhaust valves) of allcylinders.

As such, the motor may rotate the engine such that each cylinder of theengine is substantially sealed from the atmosphere. To elaborate, ifeach cylinder of the engine includes a single intake valve and a singleexhaust valve (and no additional intake or exhaust valves), the enginemay be rotated by the motor such that at least one of the single intakevalve and the single exhaust valve of each cylinder is fully closed. Inanother example, if each cylinder of the engine includes two intakevalves and two exhaust valves, the crankshaft may be rotated such thatboth intake valves of each cylinder are closed or both exhaust valves ofeach cylinder are closed. Effectively, each cylinder may be sealed andisolated from the atmosphere. Alternatively, all intake valves and allexhaust valves of each cylinder may be fully closed.

By closing all the intake valves (or all exhaust valves) of eachcylinder of the engine, the intake manifold may also be isolated fromthe atmosphere. Closing all the intake and/or exhaust valves to seal theintake manifold from the atmosphere may enable a more accuratedetermination of change in the vacuum in the intake manifold. Further,the desired level of vacuum (e.g., pre-determined level of vacuum) maybe trapped inside the intake manifold. Next, at 510, changes in themanifold vacuum are monitored, e.g., by monitoring the MAP sensoroutput. Further still, the manifold vacuum may be monitored for aspecific pre-determined duration D. The pre-determined duration D may bebased on an average duration of an idle stop, for example. In thedepicted example, the pre-determined duration in routine 500 is the sameas the pre-determined duration in routine 400. In alternative examples,pre-determined duration for a hybrid vehicle may be different from apre-determined duration of a non-hybrid vehicle. Similarly,pre-determined duration of vacuum monitoring in a hybrid vehicle may bedistinct from a pre-determined duration in a vehicle equipped with astart-stop system.

Next, at 512, routine 500 determines if vacuum levels in the intakemanifold have reduced. Specifically, routine 500 determines if thevacuum levels in the intake manifold are lower than a threshold level,Threshold_L, within pre-determined duration D. The threshold level,Threshold_L, may be the same as the threshold level of routine 400. Inalternative examples, the threshold level of vacuum may be different fora hybrid vehicle relative to the threshold level for a non-hybridvehicle.

If it is determined that the manifold vacuum level is lower than thethreshold level, Threshold_L within pre-determined duration D, routine500 progresses to 516 to indicate leaks are present in the intakemanifold and at 518, a MIL may be activated to notify the vehicleoperator. As such, the controller may also adjust one or more of fuelinjection amount and fuel injection timing in response to the indicationof manifold leaks.

However, if the vacuum level in the intake manifold remains higher thanthe threshold level, Threshold_L, within the pre-determined duration D,routine 500 proceeds to 514 to not indicate any leaks in the intakemanifold. As such, no indication may be provided to the vehicleoperator. Further, in some examples, the controller may activatealternate diagnostic methods to determine the source of leaner thandesired engine conditions.

Next, at 520, routine 500 determines if a hot engine start isanticipated. A hot engine start may be expected when the engine isactivated following an idle stop condition, e.g., when the vehicleequipped with the start-stop system is stopped at a traffic light. If ahot engine start is expected, routine 500 continues to 524 to shift theposition of the crankshaft in the engine to a position that enables ahot engine start. Specifically, the motor may be employed to rotate thecrankshaft either forward or backward to a position enabling the hotengine start. For example, the engine may be rotated such that at leastone cylinder of the engine is in a compression stroke to enable a rapidrestart. In another example, the position of the engine at 506 may bethe same position desired for the hot start. Accordingly, the engineposition may not be changed after the leak test is completed.

If, however, a hot engine start is not anticipated, routine 500progresses to 522 to adjust the engine via the motor to a position thatenables a cold engine start. For example, the controller may determinethat the engine has been shut down for a longer duration such that asubsequent engine start will be a cold start. Herein, the motor mayrotate the crankshaft either forward or backward to a position thatenables cold start. For example, the position of the intake and exhaustvalves, and piston positions of cylinders of the engine may be adjustedsuch that intake manifold pressure is reduced as the engine starts up.In another example, the position of the engine at 506 may be suitablefor a subsequent engine cold start. Accordingly, the position of theengine may not be changed from that at 506 in routine 500.

It will be noted that in some examples the motor may adjust the engine(and crankshaft) after completion of the intake manifold leak test to aposition that is different from the position of the engine during theleak test of the intake manifold. To elaborate, the position of thecrankshaft (and engine) at 506 of routine 500 may be distinct from theposition of the engine (and crankshaft) at either 524 or 522 of routine500. In other examples, the position of the engine (and the crankshaft)may not be adjusted after completion of the leak test in the intakemanifold. As such, the position of the engine resulting in all intakevalves (or all exhaust valves) being closed may be retained after theleak test of the intake manifold is completed.

Next, at 526, routine 500 restores the position of other valves of theengine including the position of the intake throttle, the EGR valve, andthe CPV. For example, the intake throttle may be transitioned from thefully closed position during the leak test of the intake manifold to amore open position after completion of the leak test of the intakemanifold. In the example wherein other diagnostic approaches areactivated to diagnose for lean engine conditions, the positions of theintake throttle, the EGR valve, and the CPV may be adjusted based on thediagnostic approaches used.

In this manner, an example hybrid vehicle system may comprise an engineincluding a first cylinder and a second cylinder, the first cylinderhaving a first intake valve and a first exhaust valve, and the secondcylinder including a second intake valve and a second exhaust valve, anintake manifold fluidically communicating with each of the firstcylinder and the second cylinder via the first intake valve and thesecond intake valve respectively, a motor coupled to a battery, agenerator also coupled to the battery, vehicle wheels propelled usingtorque from one or more of the engine, the generator, and the motor, anintake throttle controlling air flow into the intake manifold, apressure sensor coupled to the intake manifold, and a fuel systemincluding a fuel tank coupled to a canister, the canister coupled to theintake manifold via a purge valve.

The example hybrid vehicle system may also include a controller withcomputer-readable instructions stored in non-transitory memory for, inresponse to determining lean engine conditions, initiating a leak testin the intake manifold during a subsequent engine rundown to enginestop. The initiation of the leak test may include closing each of theintake throttle and canister purge valve, generating a vacuum in theintake manifold, closing one of the first intake valve and the firstexhaust valve of the first cylinder while simultaneously closing one ofthe second intake valve and the second exhaust valve of the secondcylinder responsive to vacuum in the intake manifold attaining apre-determined level, and monitoring changes in the vacuum in the intakemanifold over a pre-determined duration. The controller may includeinstructions for indicating a leak in the intake manifold when vacuum inthe intake manifold decreases to a threshold level within thepre-determined duration. Closing one of the first intake valve and thefirst exhaust valve of the first cylinder while simultaneously closingone of the second intake valve and the second exhaust valve of thesecond cylinder may comprise rotating the engine via the motor to afirst position where one of the first intake valve and the first exhaustvalve of the first cylinder and one of the second intake valve and thesecond exhaust valve of the second cylinder are fully closed. Thus, theintake manifold may be sealed from the atmosphere. The controller mayinclude additional instructions for rotating the engine via the motor toa second position after completing the leak test in the intake manifold,the second position being different from the first position. The secondposition may be based on whether the engine may experience a subsequenthot start or a cold start. In alternative examples, the second positionmay be the same as the first position. Accordingly, in these alternativeexamples, the controller may not rotate the engine via the motor aftercompletion of the leak test in the intake manifold. The controller mayinclude further instructions for not indicating the leak in the intakemanifold in response to vacuum in the intake manifold remaining higherthan the threshold level within the pre-determined duration.

Thus, an intake manifold in an engine may be checked for leaks with amethod that is less complex and more reliable. A camless enginefeaturing electrical or electro-mechanical actuators for each of theintake valves and the exhaust valves of each cylinder of the camlessengine may enable this more reliable method. Alternatively, the samemethod may be employed for engines including cams and camshafts forvalve operation by using extra valves that can substantially isolate theintake manifold from the atmosphere. Further still, a motor in a hybridvehicle or a motor in a vehicle with a start-stop system may be used torotate the engine to seal the intake manifold from the atmosphere.Herein, the engine may not be camless.

The leak test is initiated during an engine shut down (to rest) onlyafter lean engine conditions are detected. Vacuum is generated in theintake manifold prior to an anticipated engine shut down by terminatingall air flow into the intake manifold. For example, the intake throttlemay be adjusted to fully closed (from an open position). Further, othersources of intake air such as EGR and canister purge may also bediscontinued. Once a desired level of vacuum (or negative pressure) isachieved in the intake manifold due to piston motion within thecylinders of the engine, the intake manifold is isolated from theatmosphere by closing all intake valves of each cylinder of the engine.Alternatively, all exhaust valves of all cylinders may be fully closedto seal the intake manifold from the atmosphere. By sealing the intakemanifold from the atmosphere only after the desired level of vacuum (orpre-determined vacuum level) is attained in the intake manifold, theleak test may be reliably repeated. Further, the controller may notstore different rates of vacuum decrease in its memory since the samepre-determined level of vacuum (Threshold_P) is attained in the intakemanifold before monitoring for leaks.

The sealed intake manifold may now be observed for changes in vacuumlevel within a pre-determined specific duration. If the vacuum level inthe intake manifold reduces to below a threshold level (e.g.,Threshold_L) within the specific duration, the intake manifold may haveleaks. However, if the vacuum in the intake manifold remains higher thanthe threshold level in the pre-determined duration, the intake manifoldmay be substantially robust without leaks.

Turning now to FIG. 6, it portrays map 600 depicting an example leaktest performed in an engine in a non-hybrid vehicle. Further, thevehicle may also not be equipped with a start-stop system. Furtherstill, the engine may be a camless engine including cylinders withcamless intake valves. The cylinders may also include camless exhaustvalves. Map 600 includes indication of intake manifold (IM) leak at plot602, initiation of the IM leak test at plot 604, vacuum level in theintake manifold at plot 606, status of all intake valves of allcylinders of the engine at plot 608, status of the canister purge valve(CPV) at plot 610, position of the intake throttle at plot 612, enginespeed at plot 614, and a position of a gear selector at plot 616. Allthe above are plotted against time on the x-axis. It will be noted thattime increases from the left of the x-axis to the right of the x-axis.Line 603 represents atmospheric pressure (or barometric pressure). Line605 represents the threshold level of vacuum (Threshold_L of routines400 and 500) in the intake manifold. Specifically, line 605 representsthe threshold level of vacuum for determining if a leak is present inthe intake manifold of the engine. Line 607 represents thepre-determined vacuum level (Threshold_P of routine 400) in the intakemanifold. To elaborate, the pre-determined vacuum in the intake manifoldis the level of vacuum that is generated in the intake manifold beforeclosing all intake valves of all cylinders of the engine. As shown, thepre-determined level of vacuum, Threshold_P (line 607) may be a higheramount of vacuum than the threshold level (line 605) of vacuum fordetermining a leak in the intake manifold.

The position of the gear selector includes only two positions: drive andpark, though other positions are available (including reverse, neutral,etc.). It will also be noted that the status of the intake valves of allcylinders at plot 608 can vary between a variable status and an allclosed status. The variable status represents the variability of intakevalve position during an engine cycle. Based on the cylinder stroke, theposition of the respective intake valves may vary between fully open,fully closed, and any position therebetween.

Prior to t1, the vehicle may be operating with the gear selector in the“drive” position. Further, engine speed may be lower with the intakethrottle at a mostly closed (or partly open) position. At this positionof the intake throttle, a lower amount of air flow may be drawn into theintake manifold. The manifold vacuum may be relatively high since theintake throttle is mostly closed. Further, the CPV may be closed. Thestatus of the intake valves of the cylinders may be variable based onthe stroke in each cylinder during engine operation.

At t1, the throttle may be transitioned to fully open from the partlyopen position in response to a sudden increase in torque demand. Forexample, the vehicle may be accelerating to merge with traffic on ahighway. In response to the fully open position of the intake throttle,engine speed rises temporarily and manifold vacuum reduces tosubstantially atmospheric pressure. At t2, the engine speed reduces asthe intake throttle position is adjusted to between fully open and fullyclosed. For example, the vehicle may now be cruising on the highway andengine speed reduces responsive to the cruising conditions. As such, theposition of the intake throttle may be halfway between the fully openposition and the fully closed position, allowing a desired amount of airto flow into the intake manifold. Since the intake throttle ishalf-closed (relative to fully open between t1 and t2), manifold vacuumincreases and stabilizes. The steady state cruising conditions enable anopening of the CPV at t2 to allow purging of stored fuel vapors from afuel system canister.

At t3, engine speed may reduce as the intake throttle is adjustedtowards a more closed position. For example, the vehicle may be slowingdown to come to rest. At t4, the vehicle operator shifts the gearselector from “drive” to “park”. As such, an engine shut down may beimminent. Accordingly, a leak test may be initiated at t4. Though notspecified in the example depicted in map 600, the leak test may beinitiated only after diagnosing leaner than desired engine conditions(as described earlier in reference to FIG. 3). In response to theimminent engine shut down, the desired intake manifold leak test may beinitiated by adjusting the intake throttle to the fully closed positionat t4. Simultaneously, the CPV may also be adjusted fully closed todiscontinue the flow of purged vapors and air into the intake manifold.In response to the termination of air flow into the intake manifold andthe rotation of the engine as it spins down to rest, manifold vacuumincreases as shown by plot 606.

At t5, the level of manifold vacuum reaches the pre-determined vacuumlevel represented by line 607. As an example, the pre-determined vacuumlevel may be 10 inches of mercury. Upon attaining the pre-determinedvacuum in the intake manifold, all the intake valves of all cylinders ofthe engine may be shut closed. Accordingly, any further motion of theengine (and pistons in the cylinders) may not affect the level of vacuumin the intake manifold. In other words, the intake manifold may besealed from the atmosphere at t5. As shown by plot 614, even though theengine speed comes to rest after t5, manifold vacuum does not increasefurther after t5. It will be appreciated that the example leak test ofmap 600 only shows closing all the intake valves of all cylinders of theengine. In other examples, all exhaust valves of all cylinders of theengine may be shut closed in response to manifold vacuum attaining thepre-determined vacuum level.

As such, the vacuum level in the intake manifold may be observed aftert5. Specifically, the intake manifold vacuum levels may be monitored fordetermining intake manifold leaks after all the intake valves are closed(plot 608) at t5. Further, the intake manifold vacuum levels may bemonitored for the leak check for a pre-determined duration D after allthe intake valves are closed (plot 608) at t5. The pre-determinedduration D may last from t5 until t6, as shown on map 600. As depictedby plot 606, manifold vacuum decreases slightly from the pre-determinedvacuum level (line 607) in the pre-determined duration D. However, thisdecrease in manifold vacuum is not significant. As such, manifold vacuumremains higher than threshold level, Threshold_L, represented by line605, as pre-determined duration D ends. Thus, no leaks may be present inthe intake manifold, and no leaks are indicated at t6 (plot 602).Further, the leak test may be terminated at t6. At the same time, theposition of the intake valves of the cylinders of engine may be restoredto a desired position (e.g., variable) for a subsequent engine start.Optionally, some of the intake valves of some cylinders of the enginemay be maintained closed as shown by dashed section 609. The CPV may beretained at its closed position and the intake throttle may be adjustedto partly open.

Between t6 and t7, a certain length of time of vehicle operation maypass. In one example, the duration between t6 and t7 may be 48 hours. Inanother example, the duration may be 1 week. At t7, therefore, a drivecycle distinct from the drive cycle between t1 and t6 may be occurring.As such, the vehicle may be moving with the engine operating at a steadystate (e.g., medium) speed with the gear selector in the “drive”position. The intake throttle position may be about midway between fullyclosed and fully open allowing sufficient air flow into the intakemanifold. As shown, the CPV may be opened to purge stored fuel vaporsfrom the canister. Further, the intake valves of all the cylinders maybe operational. Thus, the position of each intake valve of each cylinderof the engine may be variable based on the respective cylinder stroke.Manifold vacuum level may be lower since the intake throttle is openallowing adequate air flow into the intake manifold.

At t8, the vehicle may slow down as depicted by the reduction in enginespeed and the decrease in the opening of the intake throttle.Specifically, the intake throttle position may be adjusted from midwaybetween fully open and fully closed to a mostly closed position. As suchthe vehicle may be slowing down to a stop. At t9, the gear selector istransitioned from the “drive” position to the “park” position indicatingan imminent engine shut down. Accordingly, another leak test for theintake manifold may be initiated at t9. Though not specifically shown,the leak test may be initiated in response to detection of lean engineconditions prior to the engine shut down. Thus, the leak test may beinitiated during an engine rundown to engine stop.

The leak test of the intake manifold is initiated at t9 bysimultaneously closing each of the intake throttle and the CPV, thus,terminating air flow into the intake manifold. Specifically, the intakethrottle is adjusted to the fully closed position at t9, and the CPV isalso fully closed at t9. Though not shown, other valves and passagesthat allow air to enter the intake manifold, such as an EGR valve, mayalso be closed to block entry of air into the intake manifold once theleak test in initiated.

In response to closing each of the intake throttle and the CPV, vacuumin the intake manifold rises (plot 606) after t9. At t10, vacuum buildup in the intake manifold reaches the pre-determined vacuum level (line607). Electro-mechanical actuators may then adjust all the intake valvesof all cylinders of the engine to their respective fully closedpositions in response to intake manifold vacuum levels rising to thepre-determined level, e.g., Threshold_P of FIG. 4. Thus, the intakemanifold may now be substantially sealed from the atmosphere and maycontain vacuum at the pre-determined vacuum level at t10. It will benoted that the engine may continue to spin for a short time after allthe intake valves are closed (plot 614). Thus, the intake valves of allcylinders of the engine may be closed before the engine shuts down torest.

The controller may now monitor the intake manifold vacuum levels for thepre-determined duration D. Specifically, the controller may observechanges in the level of vacuum in the intake manifold. For example,leaks in the intake manifold may allow air into the intake manifoldcausing a decrease in the level of intake manifold vacuum. Between t10and t11 the level of vacuum may be monitored for the pre-determinedduration D. As shown in map 600, manifold vacuum levels reduce in thepre-determined duration D such that at t11, the level of manifold vacuumis lower than the threshold level, Threshold_L (line 605). Accordingly,a leak in the intake manifold may be indicated at t11 (plot 602). Thus,the leak test may be completed at t11 (plot 604), and various valves maybe restored to their default or desired positions. For example, some ofthe intake valves of certain cylinders of the engine may be adjustedopen at t11. At the same time, remaining intake valves may be maintainedclosed as depicted by the dashed line 611. The CPV and the intakethrottle may be maintained fully closed. Alternatively, the intakethrottle may be adjusted to a partly open position at t11 as shown bydashed line 613.

In this manner, an example method may comprise adjusting a position ofan intake throttle to generate vacuum in an intake manifold of theengine responsive to an anticipated shut down of an engine, closing eachcamless intake valve of each cylinder of the engine before the engineshuts down to rest, monitoring the vacuum for a pre-determined duration(duration D), and indicating a leak in the intake manifold in responseto the vacuum decreasing below a threshold (e.g., Threshold_L or line605 of map 600). The position of the intake throttle may be adjustedresponsive to diagnosing lean conditions in the engine. Adjusting theposition of the intake throttle may include adjusting the intakethrottle to a fully closed position (such as at t4 or t9 of map 600),such that air flow into the intake manifold is discontinued orterminated. The method may further comprise adjusting each of an exhaustgas recirculation valve and a canister purge valve to a respectiveclosed position (such as at t4 and t9 of map 600) simultaneously withadjusting the position of the intake throttle to the fully closedposition. The anticipated shut down of the engine may be determined whena gear selector is transitioned from a non-parked position (such as a“drive” position) to a parked position. As such, each camless intakevalve of each cylinder of the engine may be closed in response to thevacuum in the intake manifold attaining a pre-determined level (e.g.,Threshold_P of routine 400). Further, each camless intake valve of eachcylinder of the engine may be actuated (e.g., closed, opened) via anelectro-mechanical actuator. The method may further comprise applyingleftover vacuum from the intake manifold to diagnose a fuel system forleaks after indicating the leak in the intake manifold (as shown inroutine 400). Thus, the method may include indicating the leak in theintake manifold when all the intake valves are closed.

FIG. 7 includes an example leak test for an intake manifold (IM) of anengine included in a hybrid vehicle. Map 700 of FIG. 7 includesinitiation of the IM leak test at plot 702, vacuum level in the intakemanifold at plot 704, rotation of the engine via a first motor at plot706, status of all the intake valves of all cylinders of the engine atplot 708, engine speed at plot 710, position of the intake throttle atplot 712, status of the engine (on/off) at plot 714, and status of agenerator (also termed, motor) at plot 716. All the above are plottedagainst time on the x-axis. It will be noted that time increases fromthe left of the x-axis to the right of the x-axis. Further, the hybridvehicle comprises two motors, or a motor and a generator. To elaborate,the first motor that is utilized to rotate the engine may be distinctfrom the second motor or generator propelling the vehicle during anengine-off mode.

Line 703 represents the pre-determined vacuum level (Threshold_P ofroutine 400) in the intake manifold. Line 705 represents the thresholdlevel of vacuum (Threshold_L of routine 500) in the intake manifold.Specifically, line 705 represents the threshold level of vacuum fordetermining if a leak is present in the intake manifold of the engine.Line 707 represents atmospheric pressure (or barometric pressure). Toelaborate, the pre-determined vacuum, Threshold_P, in the intakemanifold is the level of vacuum that is generated in the intake manifoldbefore closing all intake valves of all cylinders of the engine. Asshown, the pre-determined level of vacuum, Threshold_P (line 703) may bea higher amount of vacuum than the threshold level (line 705) of vacuumfor determining a leak in the intake manifold.

Prior to t1, the hybrid vehicle may be propelled primarily by the enginedepicted by the engine status at “on” and the motor status at “off”. Theintake throttle may be at position that is about halfway between thefully closed and fully open positions. As such, the vehicle may becruising on a highway with a moderate engine speed (plot 710). Theintake valves of the cylinders of the engine may be at variablepositions (plot 708) since the engine is operational. As noted earlierin reference to FIG. 6, the status of the intake valves of all cylindersat plot 708 can vary between a variable status and an all closed status.The variable status represents the variability of intake valve positionduring an engine cycle. Based on the cylinder stroke during engineoperation, the position of the respective intake valves may vary betweenfully open, fully closed, and any position therebetween.

Prior to t1, the vacuum levels in the intake manifold may be relativelylower (or shallow) since the intake throttle is allowing a substantialamount of air into the intake manifold. At t1, the intake throttle maybe adjusted to a more closed position reducing the amount of air flowinginto the intake manifold. For example, the vehicle may be slowing downas it approaches an exit of the highway. Engine speed may reduce andintake manifold vacuum levels may rise with the change in position ofthe intake throttle. An engine shut down may be imminent as the vehiclemay be subsequently driving on city streets where motor torque may bemore efficient than engine torque. Accordingly, an intake manifold leaktest may be initiated at t2. Though not specifically shown, leaner thandesired engine conditions may be detected in the engine prior to theengine shut down inducing the intake manifold leak test to be performedat the ensuing engine shut down.

Therefore, at t2, the intake throttle may be adjusted to fully closedposition and the engine may be shut down (plot 714) while simultaneouslythe second motor or generator is activated. As the engine rotates torest after t2, intake manifold vacuum rises with the closure of theintake throttle. By t3, the intake manifold vacuum is at thepre-determined vacuum level (line 703) and the engine is at rest orengine stop (plot 710). In response to the intake manifold vacuumreaching the pre-determined vacuum level, the first motor may rotate thecrankshaft of the engine (plot 706) to a position that fully closes allintake valves (plot 708) of all cylinders of the engine. In one example,the first motor may rotate the engine in a forward direction if theforward direction enables a faster closing of all the intake valves. Inanother example the first motor may rotate the engine in a backwarddirection if the backward direction enables a faster closing of all theintake valves.

Thus, at t3, all the intake valves of all the cylinders of the enginemay be fully closed isolating the intake manifold from the atmosphere.The vacuum level in the intake manifold may be monitored for thepre-determined duration D (between t3 and t4) to observe changes in thelevel of the vacuum. It will be appreciated that the pre-determinedduration for the hybrid vehicle in some examples may be different fromthe pre-determined duration utilized in the leak test of a non-hybridvehicle. As shown, the level of vacuum in the intake manifold reducesduring the pre-determined duration D. At t4, the level of vacuum in theintake manifold is lower than the threshold level (line 705).Accordingly, a leak may be present in the intake manifold, and may beindicated by the controller (not shown in FIG. 7). The leak test may nowbe complete (plot 702) and the first motor may rotate the engine at t4to a different position from that at t3. Specifically, the first motormay rotate the engine to a different position based on a desiredposition of the intake valves in anticipation of a subsequent enginestart. In another example, the first motor may not rotate the engine asshown at t4 and the engine may be retained in the position it is at t3.

In this way, an intake manifold of an engine may be diagnosed for leaks.Vacuum is generated in the intake manifold during an impending engineshut down. Once a desired (pre-determined) level of vacuum is attained,the intake manifold may be sealed from the atmosphere by closing allintake valves (or all exhaust valves) of all cylinders of the engine.The technical effect of isolating the intake manifold from theatmosphere during the leak test is a more accurate and less complex leaktest. By ensuring that the intake manifold achieves the pre-determinedlevel of vacuum during every leak test, the leak test may be performedwithout referencing multiple look-up tables including different rates ofchange in vacuum. The leak test may be more reliably performedrepetitively by generating the pre-determined level of vacuum each timethe leak test is activated. As such, the leak test may be simpler andmay provide more accurate results enabling improved performance of theengine.

In another representation, an example method for a camless engine maycomprise generating a vacuum in an intake manifold of the camless engineas the camless engine spins to rest, isolating the intake manifold fromatmosphere by closing each intake valve of each cylinder of the camlessengine after the vacuum in the intake manifold exceeds a vacuumthreshold, indicating a leak in the intake manifold when the vacuumdecreases to lower than a threshold level, and applying leftover vacuumfrom the intake manifold to test a fuel system for leaks, the fuelsystem coupled to the engine.

In yet another representation, an example hybrid vehicle system maycomprise an engine, a cylinder of the engine having an intake valve andan exhaust valve, an intake manifold fluidically communicating with thecylinder via the intake valve, a motor coupled to a battery, a generatoralso coupled to the battery, vehicle wheels propelled using torque fromone or more of the engine, the generator, and the motor, an intakethrottle controlling air flow into the intake manifold, a pressuresensor coupled to the intake manifold, an exhaust gas recirculation(EGR) passage fluidically coupling an exhaust passage to the intakemanifold via an EGR valve, and a fuel system including a fuel tankcoupled to a canister, the canister coupled to the intake manifold via acanister purge valve.

The example hybrid vehicle system may also include a controller withcomputer-readable instructions stored in non-transitory memory for, inresponse to determining lean engine conditions, initiating a leak testin the intake manifold during a subsequent engine rundown to enginestop. The initiation of the leak test may include closing each of theintake throttle, the EGR valve, and canister purge valve, generating avacuum in the intake manifold, closing one of the intake valve and theexhaust valve of the cylinder responsive to vacuum in the intakemanifold attaining a pre-determined level, and monitoring changes in thevacuum in the intake manifold over a pre-determined duration. Thecontroller may include instructions for indicating a leak in the intakemanifold when vacuum in the intake manifold decreases to or below athreshold level within the pre-determined duration. The intake valveand/or the exhaust valve of the cylinder may be closed by rotating theengine via the motor to a first position such that the intake valveand/or the exhaust valve of the cylinder is fully closed. Thus, theintake manifold may be sealed from the atmosphere. The controller mayinclude additional instructions for rotating the engine via the motor toa second position after completing the leak test in the intake manifold,the second position being different from the first position. The secondposition may be based on whether the engine may experience a subsequenthot start or a cold start.

In a further representation, an example system may comprise an engine, acylinder of the engine having an intake valve, the intake valve actuatedindependently of rotation of the engine, an intake manifold fluidicallycommunicating with the cylinder via the intake valve, an intake throttlecontrolling air flow into the intake manifold, a pressure sensor coupledto the intake manifold, an exhaust gas recirculation (EGR) passagefluidically coupling an exhaust passage to the intake manifold via anEGR valve, and a fuel system including a fuel tank coupled to acanister, the canister coupled to the intake manifold via a canisterpurge valve. The example system may also include a controller withcomputer-readable instructions stored in non-transitory memory for, inresponse to determining lean engine conditions, initiating a leak testin the intake manifold during a subsequent engine shut down to rest. Theinitiation of the leak test may include closing each of the intakethrottle, the EGR valve, and the canister purge valve, and generating avacuum in the intake manifold. Further, responsive to vacuum in theintake manifold attaining a pre-determined level, the intake valve ofthe cylinder may be closed to seal the intake manifold from theatmosphere, and changes in the vacuum in the intake manifold may bemonitored over a pre-determined duration. The controller may includeinstructions for indicating a leak in the intake manifold when vacuum inthe intake manifold decreases to or below a threshold level within thepre-determined duration. The intake valve of the cylinder may be closedby actuating an electro-mechanical actuator.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A method for an engine, comprising: adjusting all intake valvesclosed in each cylinder of the engine responsive to vacuum in an intakemanifold reaching a pre-determined vacuum during engine shut down; andindicating a leak in the intake manifold based on a change in a level ofvacuum in the intake manifold.
 2. The method of claim 1, wherein thechange in the level of vacuum in the intake manifold includes a decreasein the level of vacuum from the pre-determined vacuum, and wherein theleak is indicated when the level of vacuum decreases below a thresholdlevel.
 3. The method of claim 1, wherein the vacuum in the intakemanifold is produced by closing an intake throttle and discontinuingflow of air into the intake manifold.
 4. The method of claim 3, whereinthe intake throttle is closed in response to determining an impendingengine shut down.
 5. The method of claim 4, wherein the impending shutdown is determined when a gear selector is shifted to a parked position.6. The method of claim 3, further comprising producing vacuum in theintake manifold by closing each of an exhaust gas recirculation valveand a canister purge valve in response to an impending engine shut down.7. The method of claim 1, wherein all intake valves of each cylinder ofthe engine are closed via an electro-mechanical actuator.
 8. The methodof claim 1, wherein the engine is arranged within a hybrid electricvehicle, and wherein all intake valves of each cylinder of the engineare closed by rotating the engine via a generator to a position suchthat all intake valves of each cylinder of the engine are fully closed.9. The method of claim 1, further comprising applying leftover vacuum inthe intake manifold to a fuel system for a leak check in the fuel systemafter indicating the leak in the intake manifold.
 10. A method,comprising: adjusting a position of an intake throttle to generatevacuum in an intake manifold of an engine responsive to an anticipatedshut down of the engine; closing each camless intake valve of eachcylinder of the engine before the engine shuts down to rest; monitoringthe vacuum for a pre-determined duration; and indicating a leak in theintake manifold in response to the vacuum decreasing below a threshold.11. The method of claim 10, wherein the position of the intake throttleis adjusted responsive to diagnosing lean conditions in the engine, andwherein adjusting the position of the intake throttle includes adjustingthe intake throttle to a fully closed position.
 12. The method of claim11, further comprising adjusting each of an exhaust gas recirculationvalve and a canister purge valve to a respective closed positionsimultaneously with adjusting the position of the intake throttle to thefully closed position.
 13. The method of claim 10, wherein theanticipated shut down of the engine is determined when a gear selectoris transitioned from a non-parked position to a parked position.
 14. Themethod of claim 10, wherein each camless intake valve of each cylinderof the engine is closed in response to the vacuum in the intake manifoldattaining a pre-determined level.
 15. The method of claim 14, whereineach camless intake valve of each cylinder of the engine is actuated viaan electro-mechanical actuator.
 16. The method of claim 10, furthercomprising applying leftover vacuum from the intake manifold to diagnosea fuel system for leaks after the pre-determined duration.
 17. A hybridvehicle system, comprising: an engine including a first cylinder and asecond cylinder, the first cylinder having a first intake valve and afirst exhaust valve, and the second cylinder including a second intakevalve and a second exhaust valve; an intake manifold fluidicallycommunicating with each of the first cylinder and the second cylindervia the first intake valve and the second intake valve respectively; amotor coupled to a battery; a generator coupled to the battery; vehiclewheels propelled using torque from one or more of the engine, thegenerator, and the motor; an intake throttle controlling air flow intothe intake manifold; a pressure sensor coupled to the intake manifold; afuel system including a fuel tank coupled to a canister, the canistercoupled to the intake manifold via a canister purge valve; and acontroller with computer-readable instructions stored in non-transitorymemory for: in response to determining lean engine conditions,initiating a leak test in the intake manifold during a subsequent enginerundown to engine stop by closing each of the intake throttle andcanister purge valve; generating a vacuum in the intake manifold;closing one of the first intake valve and the first exhaust valve of thefirst cylinder while simultaneously closing one of the second intakevalve and the second exhaust valve of the second cylinder responsive tovacuum in the intake manifold attaining a pre-determined level; andindicating a leak in the intake manifold when vacuum in the intakemanifold decreases to a threshold level within a pre-determinedduration.
 18. The hybrid vehicle system of claim 17, wherein closing oneof the first intake valve and the first exhaust valve of the firstcylinder while simultaneously closing one of the second intake valve andthe second exhaust valve of the second cylinder includes rotating theengine via the motor to a first position where one of the first intakevalve and the first exhaust valve of the first cylinder and one of thesecond intake valve and the second exhaust valve of the second cylinderare fully closed.
 19. The hybrid vehicle system of claim 18, wherein thecontroller includes additional instructions for rotating the engine viathe motor to a second position after completing the leak test in theintake manifold, the second position being different from the firstposition.
 20. The hybrid vehicle system of claim 17, wherein thecontroller includes additional instructions for not indicating the leakin the intake manifold in response to vacuum in the intake manifoldremaining higher than the threshold level within the pre-determinedduration.